Colorectal cancer is common in many Western countries, and this is associated with diets high in animal fat and meat. It is the second most common form of cancer and the second most important cause of cancer-related death. The incidence of colorectal cancer is also rising in Asia, including Korea and Japan, where colorectal cancer was less common than in the Western world, owing to the Westernization of the diet. A recent survey (2002), conducted by the Korean National Statistical Office, showed that colorectal cancer is the fourth most common cause of cancer death in Korea, after cancer of the lung, stomach and liver. Various methods including fecal occult blood test and colonoscopy are currently used for screening colorectal cancer and increase the rates of detection of early-stage cancer. However, there are few biological markers which can be used for prognosis and to determine suitable therapy for colorectal cancer. Since to date no method capable of accurately diagnosing and staging cancer has been found, a colorectal cancer diagnosis is obtained using a variety of screening methods, including doctor's examination, histological examination, cytological examination, endoscopy, tumor marker detection, imaging test and nuclear medical examination. A tumor marker test is used to screen for and diagnose a specific type of cancer by detecting a tumor marker in blood, tissue and urine specimens. However, since many tumor markers are elevated or detected in biological specimens from individuals not afflicted with cancer, a tumor marker test is not reliable enough to detect and diagnose cancer.
Colorectal cancer is typically screened using common traditional procedures, a guaiac-based fecal occult blood test (FOBT) and colonoscopy. With the recent advances in molecular biology, cyclooxygenase 2 and SFRP2 methylation are becoming known as novel markers for screening colorectal cancer. Carcinoembryonic antigen (CEA) is a glycoprotein that was first identified in 1965 and is detected in colon carcinoma and embryonic colonic mucosa. CEA is considered to be a fetal antigen that is normally present in embryonic and fetal digestive tissues between two and six months and disappears after birth. However, it may reappear in adults who develop colorectal carcinoma and several other neoplastic conditions, including gastrointestinal, pancreatic and lung carcinomas. Due to its reappearance in malignant tissues, CEA is deemed valuable as a marker to help diagnose cancer, to monitor patients who have undergone surgery, or to monitor patients' response to treatment. When the serum CEA level is high before surgery in colorectal cancer or stomach cancer, patients are expected to have a high risk of recurrence. Thus, the CEA level seems to be a valuable prognostic indicator. Since the CEA level is increased in colorectal cancer and also in several other types of cancer in the pancreas (60-90%), stomach (40-600), lung (60-75%), breast (20-50%), and the like, it is commonly used as a broad-spectrum tumor marker. In particular, in colorectal cancer, according to the degree of tumor invasion and spread, CEA levels are elevated in 20-40% of tumors limited to the bowel wall and in 80-90% of tumors metastasized to the liver and other organs. When the cancer has metastasized to the liver, CEA levels sharply rise. Thus, CEA levels are monitored to determine the prognosis of patients having colorectal cancer or to follow up on patients after surgery. In addition to in malignant tumors, Elevated CEA levels occur in various benign diseases including liver cirrhosis, alcoholic hepatitis, pancreatitis, and ulcerative colitis. Colorectal cancer can be sometimes associated with known risk factors. These include increasing age and smoking, which is modifiable.
As another tumor marker, carbohydrate antigen 19-9 (CA 19-9) was defined initially by a monoclonal antibody isolated from mice immunized with a human colorectal carcinoma cell line, which expresses an antigen that is strongly positive in pancreatic ductal adenocarcinoma. The CA 19-9 antigen is positive in pancreatic cancer (84%), gastric cancer (35%), liver cancer (22%) and gallbladder cancer (69%), and is elevated to a high concentration of 1,000 U/ml or more in 40-50% of cancer of the pancreas and bile duct. Thus, the CA 19-9 antigen is considered useful for the early diagnosis of cancer and to help diagnose pancreatic cancer. Gastric and colorectal carcinomas are positive for CA 19-9, especially when they have metastasized to the liver. The antigen is also found in normal tissues of the pancreas and in non-cancerous cells surrounding biliary, gastric mucosal and salivary epithelial carcinomas.
Endothelial cell-specific molecule-1 (ESM-1), also called endocan. The ESM-1 secretory protein is constituted of a polypeptide of 184 amino acids corresponding to a molecular mass of about 20 kDa. Endocan is specifically associated with insulin-like growth factor to promote cell growth and proliferation, and its expression is induced by TNF-alpha and IL-1 beta. ESM-1 has been known as a diagnostic marker of sepsis (Reinhart K et al., Crit Care Clin, 2006, 22(3), 503-519, Filep J G. Crit Care Med, 2006, 34(2), 574-575, Scherpereel A et al., 2006, 34(2), 532-537). Endocan has been reported as a VEGF-A and PI3K regulated gene with increased expression in renal cancer (Rennel E et al., Exp Cell Res, 2007, 313(7):1285-1294). In lung carcinoma, contamination rates of leukaphereses were assessed by determining ESM-1 expression using immunocytochemistry and RT-PCR (L Perey et al., Br. J Cancer, 2001, 85(11):1713-21). However, there is no report disclosing the utility of ESM-1 as a diagnostic marker of colorectal cancer thorough quantitative analysis in sera and tissues. At present, ESM-1 expression levels are analyzed using general molecular biological methods, while circulating levels (protein levels) thereof are detected using Western blotting, ELISA (David B et al., J. Vasc. Res, 2000, 37, 417-425, USP 2004/0063164A1) and immunohistochemistry using antibodies. USP 2004/0063164A1, titled “Kit and Method for Detecting the ESM-1 Protein”, discloses a kit for detecting ESM-1. However, the kit is provided not for diagnosing and treating colorectal cancer, as in the present invention, but for detecting in vitro deteriorations of endothelial vascular wall by measuring ESM-1 levels.
The inventors of this application examined the biological functions of ESM-1 in colorectal cancer and evaluated its potential as a diagnostic and prognostic marker of colorectal cancer. cDNA microarray analysis and RT-PCR for ESM-1 RNA levels using tissues from normal subjects and colorectal cancer patients revealed that ESM-1 is more highly expressed in colorectal carcinoma tissues than nontumorous or normal colorectal tissues. Western blot and immunodot assays for serum ESM-1 protein levels using an antibody against ESM-1 showed higher levels of ESM-1 circulating in the serum of colorectal cancer patients compared to in the serum of normal subjects. These results indicated that ESM-1 is highly useful as a marker for the diagnosis and prognosis of colorectal cancer, leading to the present invention.